It is known in the welding industry to use electric heat-weldable fittings (also known as electrofusion fittings) formed of thermoplastic materials to fuse two pipe segments together. Such fittings generally include an electrically resistive heating coil or element positioned adjacent to the inside surfaces of the fitting which are to be welded to one or more other thermoplastic members, such as plastic pipe sections. The electrically resistive heating element typically comprises a coil of wire positioned in the thermoplastic material of the fitting, which is connected to electric contacts attached to an outside surface of the fitting. Electrofusion is an effective method for installing branch connections in pipelines, as well as for tapping into a main gas pipeline. Many vendors supply electrofusion fittings, wherein each of the fittings has a particular fusion voltage and fusion time. Such vendors often have a proprietary method for identifying the fitting to be fused or for controlling various fusion process parameters, such as time and voltage applied to the fitting.
An electrofusion controller is a known piece of equipment that is connected to an electrofusion fitting and is used to weld many types of fittings to a variety of types of plastic pipe. The electrofusion controller provides the required energy (in the form of electrical current) to properly heat the resistive element embedded in the fitting. If the amount of energy provided is too small, the fitting will not be properly bonded to the pipe. If the amount of energy provided is too large, the plastic itself will begin to degrade. If the fusion is not properly controlled, the resulting joint will be faulty and could fail a pressure test before being put into service, or worse, prematurely fail when put into service. It is therefore vital that the controller provide the correct amount of energy. The electrofusion controller provides this energy by applying a regulated voltage or current output to the resistive element in the fitting for a predetermined amount of time, or until a pre-determined amount of energy has been applied.
Since it is the job of the controller to provide a regulated voltage or current for a pre-determined amount of time, it is important that the controller is capable of accurately measuring these parameters. Important parameters include, but are not limited to: output voltage, output current, time, ambient temperature and fitting resistance. Proper calibration of the controller is therefore essential for its proper operation.
Traditionally, calibration of electrofusion controllers is carried out by a trained technician in a laboratory environment. As a result, electrofusion controllers must be shipped to a qualified facility so that calibration can be performed (typically once per year). The resultant “down time” usually lasts one or more weeks (including time in transit), which is undesirable and can cost customers shipping fees and lost productivity. As such, there is a need to reduce the down time associated with calibration and to obviate the need to ship electrofusion controllers to remote locations to perform calibration.